Association between Extremely Low-Frequency Electromagnetic Fields Occupations and Amyotrophic Lateral Sclerosis: A Meta-Analysis

<div><h3>Objectives</h3><p>To estimate the relationship between exposure to extremely low-frequency electromagnetic fields (ELF-EMF) and the risk of amyotrophic lateral sclerosis (ALS) by a meta-analysis.</p> <h3>Methods</h3><p>Through searching PubMed databases (or manual searching) up to April 2012 using the following keywords: “occupational exposure”, “electromagnetic fields” and “amyotrophic lateral sclerosis” or “motor neuron disease”, seventeen studies were identified as eligible for this meta-analysis. The associations between ELF-EMF exposure and the ALS risk were estimated based on study design (case-control or cohort study), and ELF-EMF exposure level assessment (job title or job-exposure matrix). The heterogeneity across the studies was tested, as was publication bias.</p> <h3>Results</h3><p>Occupational exposure to ELF-EMF was significantly associated with increased risk of ALS in pooled studies (RR = 1.29, 95%CI = 1.02–1.62), and case-control studies (OR = 1.39, 95%CI = 1.05–1.84), but not cohort studies (RR = 1.16, 95% CI = 0.80–1.69). In sub-analyses, similar significant associations were found when the exposure level was defined by the job title, but not the job-exposure matrix. In addition, significant associations between occupational exposure to ELF-EMF and increased risk of ALS were found in studies of subjects who were clinically diagnosed but not those based on the death certificate. Moderate heterogeneity was observed in all analyses.</p> <h3>Conclusions</h3><p>Our data suggest a slight but significant ALS risk increase among those with job titles related to relatively high levels of ELF-EMF exposure. Since the magnitude of estimated RR was relatively small, we cannot deny the possibility of potential biases at work. Electrical shocks or other unidentified variables associated with electrical occupations, rather than magnetic-field exposure, may be responsible for the observed associations with ALS.</p> </div

Characteristics of epidemiological studies of the association between occupational exposure to ELF-EMF and ALS risk.

<p>Characteristics of epidemiological studies of the association between occupational exposure to ELF-EMF and ALS risk.</p

Effects of 1800 MHz RF-EMF exposure on DNA damage and cellular functions in primary cultured neurogenic cells

<p><b>Purpose:</b> To systematically evaluate the effects of 1800 MHz radiofrequency electromagnetic fields (RF-EMF) exposure on DNA damage and cellular functions in primary cultured neurogenic cells.</p> <p><b>Materials and methods:</b> The primary cultured astrocytes, microglia and cortical neurons were exposed to RF-EMF at a SAR of 4.0 W/kg. The DNA damage was evaluated by γH2AX foci formation assay. The secretions of pro-inflammatory cytokines (TNF-α, IL-6 and IL-1β) in astrocytes and microglia, microglial phagocytic activity and neuronal development were examined by enzyme-linked immunosorbent assay, phagocytosis assay and immunofluorescent staining on microtubule-associated protein tau, microtubule-associated protein 2, postsynaptic density 95 and gephyrin, respectively.</p> <p><b>Results:</b> RF-EMF exposure did not significantly induce γH2AX foci formation in three primary cultured neurogenic cells. Furthermore, RF-EMF exposure did not significantly affect the secretion of cytokines in astrocytes and microglia, and the morphological indicators of dendrites or synapses of cortical neurons. However, the exposure significantly reduced the phagocytic activity of microglia and inhibited the axon branch length and branch number of cortical neurons.</p> <p><b>Conclusions:</b> Our data demonstrated that exposure to RF-EMF did not elicit DNA damage but inhibited the phagocytic ability of microglia and the axon branch length and branch number of cortical neurons.</p

Forest plot of the association between ALS risk and occupational exposure to ELF-EMF.

<p>Forest plot of the association between ALS risk and occupational exposure to ELF-EMF.</p

Funnel plot analysis to detect publication bias.

<p>Each point represents a separate study for the indicated association. <b>A</b> Funnel plot for all studies; <b>B</b> funnel plot for job title data; <b>C</b> funnel plot for quantitative data; <b>D</b> funnel plot for clinical examination data; <b>E</b> funnel plot for death certificate data.</p

Association of <em>Glutathione S transferases</em> Polymorphisms with Glaucoma: A Meta-Analysis

<div><h3>Background</h3><p><em>Glutathione S transferase</em> (<em>GST</em>) polymorphisms have been considered risk factors for the development of glaucoma, including primary open angle glaucoma (POAG) and other types of glaucoma. However, the results remain controversial. In this study, we have conducted a meta-analysis to assess the association between polymorphisms of <em>GSTM1</em>, <em>GSTT1</em> and <em>GSTP1</em> and glaucoma risk.</p> <h3>Methods</h3><p>Published literature from PubMed and other databases were retrieved. All studies evaluating the association between <em>GSTM1</em>, <em>GSTT1</em> and <em>GSTP1</em> polymorphisms and glaucoma risk were included. Pooled odds ratio (OR) and 95% confidence interval (CI) were calculated using random- or fixed-effects model.</p> <h3>Results</h3><p>Twelve studies on <em>GSTM1</em> (1109 cases and 844 controls), ten studies on <em>GSTT1</em> (709 cases and 664 controls) and four studies on <em>GSTP1</em> (543 cases and 511 controls) were included. By pooling all the studies, either <em>GSTM1</em> or <em>GSTT1</em> null polymorphism was not associated with a POAG risk, and this negative association maintained in Caucasian. The <em>GSTP1</em> Ile 105 Val polymorphism was significantly correlated with increased POAG risk among Caucasian in a recessive model (Val/Val <em>vs</em>. Ile/Ile+Ile/Val: OR, 1.62, 95%CI: 1.00–2.61). Interestingly, increased glaucoma risk was associated with the combined <em>GSTM1</em> and <em>GSTT1</em> null genotypes (OR, 2.20; 95% CI, 1.47–3.31), and with the combined <em>GSTM1</em> null and <em>GSTP1</em> Val genotypes (OR, 1.86; 95% CI, 1.15–3.01).</p> <h3>Conclusions</h3><p>This meta-analysis suggests that combinations of <em>GST</em> polymorphisms are associated with glaucoma risk. Given the limited sample size, the associations between single <em>GST</em> polymorphism and glaucoma risk await further investigation.</p> </div

Flow diagram of studies identification.

<p>Flow diagram of studies identification.</p

Characteristics of literatures included in the meta-analysis.

*<p>Others: including exfoliative and primary closed angle glaucoma.</p><p>Abbreviations: POAG, primary closed angle glaucoma; PCR, Polymerase chain reaction; ELISA, enzyme-linked immunosorbent assay.</p

Subgroup Analysis of the Association between <i>GSTM1</i> and <i>GSTT1</i> Polymorphisms and the Risk for Glaucoma.

*<p>Others: including exfoliative and primary closed angle glaucoma.</p>†<p>n: number of studies.</p><p>Abbreviations: POAG, primary closed angle glaucoma.</p

Funnel plots showed symmetric distribution.

<p>Log OR is plotted against the standard error of log OR for studies on <i>GSTM1</i> null (A), <i>GSTT1</i> null (B) and <i>GSTP1</i> Ile 105 Val (recessive model) (C) polymorphism. The dots represent specific studies for the indicated association.</p